1. Field of the Invention
This invention provides a nutritional supplement containing docosahexaenoic acid (DHA), lutein and anthocyanosides. The supplement is useful for improving night vision acuity, field of vision and adaptation to light.
2. Discussion of the Background
Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are omega-3 (.omega.3) polyunsaturated fatty acids (PUFA) found naturally in marine oils. Both DHA and EPA have beneficial pharmacological effects on the human cardiovascular system, the auto-immune system and the development and maintenance of the brain and retina functions. DHA is present in large amounts in the outer segments (phospholipids) or photoreceptor cells of the retina (Murphy M G, J. Nutr. Biochem. 1990, 1: 69-70). Although the role of DHA in retinal function has been questioned (See Leaf et al., Early Human Dev. 1996, 45:35-53; Weisinger et al., Lipids 1996, 31:65-70), it is widely believed to be beneficial (See Noble et al., U.S. Pat. No. 5,484,611). DHA is critical for normal retinal development, and continues to accumulate in the retina even after birth, suggesting that it is a vital nutrient Conner WE et al., World Review in Nutrition and Dietetics 1991, 66:118-32).
Antioxidants are believed to extend normal vision by preventing cataract formation (See Taylor, J. Am. Coll. Nutr. 1993, 12:138-46) and other visual disorders (Richer, J. Am. Optom. Assoc. 1996, 67:30-49). Lutein and zeaxanthin are antioxidants, belonging to a class of lipid-soluble yellow-to-red pigments known as carotenoids. In humans, lutein and zeaxanthin are major constituents of the macula lutea region of the retina, which is responsible for sharp, detailed viewing (Bone R A et al., Invest. Ophthalmol. Vis. Sci. 1993, 34:3033-40).
Anthocyanosides are a group of red to blue plant pigments, which exist as condensed products (glycosides) of anthocyanins or anthocyanidins combined usually with sugar, such as glucose, arabinose or galactose. Bilberry contains a variety of anthocyanosides including cyanidine, malvidine, delphynidine, petunidine and peonidiene. Anthocyanosides are similar in structure and function to bioflavonoids. In particular, anthocyanosides enhance the regeneration of rhodopsin or visual purple, an eye protein necessary for vision in dim light or at night. Anthocyanosides may also improve vision by enhancing the activity of metabolic enzymes in the retina. (See De Smet, P. (1983) "Vaccinium myrtillus," In Adverse Effects of Herbal Drugs, De Smet et al. eds., pp. 307-314, Berlin: Springer-Verlag; Cunio, L. Austrian J. Medicinal Herbalism 1993, 5(4):81-85; Mowrey, E. (1990) "Bilberry: For veins, eyes and nerves." In Guaranteed Potency Herbs: Next Generation Herbal Medicine, pp. 14-24, New Canaan: Keats Publishing Inc.).
Despite the recognition of the beneficial properties of DHA, antioxidants such as lutein and anthocyanosides, the American diet contains few foods which supply these nutrients. Thus, a nutritional supplement comprising these is desirable. Such a nutritional supplement is particularly useful for preventing visual disorders and for improving vision.